1. Field of the Invention
This invention relates to rotary drive assemblies and in particular to means for lubricating such assemblies having clutch and brake packs.
2. Description of the Prior Art
In one form of rotative drive assembly, a brake pack and a clutch pack are provided for controlling the delivery of driving power to a final drive, such as the final drive of the wheel or track-type vehicle. In such drive assemblies, lubricating oil is provided to the clutch pack or brakes for both cooling and lubricating the plates thereof when engaged. The clutch and brake packs may be selectively operated to effect a steering operation as by controlling the driving and braking of opposite sides of the vehicle propulsion means.
One excellent example of such a drive assembly is shown in copending U.S. patent application, Ser. No. 696,680, of Gerald E. Whitehurst, for a Modular Steering Clutch and Brake Pack, filed June 16, 1976, which application is owned by the assignee hereof, and which has issued on June 27, 1978, as U.S. Pat. No. 4,096,931.
A number of different prior art United States Letters Patent disclose means for cooling clutches and the like in such rotative drive assemblies. Illustratively, in U.S. Pat. No. 3,351,169, of Ronald M. McIndoe, a control system for hydraulically actuated friction clutches is disclosed wherein a cooling flow of lubricant is delivered to the clutch disks during partial engagement but not during disengagement thereof. A manual clutch pedal is connected through a linkage to suitable valve means of a hydraulically actuated clutch control to control the supply of fluid to the friction surfaces. The valve means includes a first portion defining a pressure regulator for modulating the pressure of and controlling the flow of clutch-engaging fluid, and a second portion for controlling the flow of clutch cooling fluid. The modulation of the valve permits the operator to obtain a desired degree of clutch engagement. The system utilizes a relatively sophisticated external valving means for effecting the desired control.
Another example of hydrodynamic and friction coupling is shown in U.S. Pat. No. 3,547,235 of Hellmut Weinrich. As disclosed therein, oil circulation is effected during a braking operation to bring about a cooling of the braking discs. In effect, a fottinger circuit is formed.
U.S. Pat. No. 3,773,157 of Franklin O. Koch, Jr. et al, discloses a clutch with coolant cut-off valve arranged to divert fluid from the friction means during disengagement thereof to eliminate viscous drag. Upon disengagement of the clutch assembly therein, a housing is moved while the valve is held in position by means of a control rod. Movement of the housing opens flow passages for providing free flow of fluid from the pressure chamber directly to the sump to provide a sharp cut-off of fluid supply to the clutch disc assembly. The result is that the space between the discs is free of oil, thereby eliminating this viscous drag. A separate diverter valve is provided in a cylindrical bore of the structure to provide the desired control.